A5013573921- Muon and positron interactions and applications
- Copper Interconnects and Reliability
- Semiconductor materials and devices
- Graphene research and applications
- Ammonia Synthesis and Nitrogen Reduction
- Ion-surface interactions and analysis
- Atomic and Molecular Physics
- Advancements in Battery Materials
- Particle accelerators and beam dynamics
- Particle Accelerators and Free-Electron Lasers
- Silicon and Solar Cell Technologies
- Membrane Separation and Gas Transport
- Muscle activation and electromyography studies
- Plasma Diagnostics and Applications
- Chemical Synthesis and Characterization
- Iterative Learning Control Systems
- Nuclear Physics and Applications
- Adaptive Control of Nonlinear Systems
- Stability and Control of Uncertain Systems
- GaN-based semiconductor devices and materials
- Gyrotron and Vacuum Electronics Research
- Synthesis and characterization of novel inorganic/organometallic compounds
- Electron and X-Ray Spectroscopy Techniques
- Fusion materials and technologies
- Radiation Detection and Scintillator Technologies
NTT (Japan)
2025
Chiba Institute of Technology
2024
Kanazawa Institute of Technology
2014-2024
National Institute of Advanced Industrial Science and Technology
2012-2023
Nippon Veterinary and Life Science University
2023
Kyushu University
1995-2022
Innovative Structural Materials Association
2019-2020
Waseda University
2015
Mie University
2012
University of Tsukuba
1985-2012
The free-volume depth profile of asymmetric polymeric membrane systems prepared by interfacial polymerization is studied using positron annihilation spectroscopy coupled with a variable monoenergy slow beam. Significant variations S, W, and R parameters from the Doppler broadened energy spectra vs incident up to 30 keV orthopositronium lifetime intensity are observed at different doping times triethylenetetraamine (TETA) reacting trimesoyl chloride (TMC) in an on modified porous...
A positron pulsing system has been constructed for variable energy lifetime spectroscopy. The consists of a reflection type chopper, sub-harmonic prebuncher, and double harmonic buncher. By operating the with an intense slow beam generated by electron linac, spectra have successfully measured in extended time range more than 45 ns good resolution (250 ps). Furthermore, Doppler broadening profiles annihilation radiations can be obtained simultaneously measurements.
Phosphorus ions were implanted in ZnO single crystals with energies of 50–380keV having total doses 4.2×1013–4.2×1015cm−2. Positron annihilation measurements reveal the introduction vacancy clusters after implantation. These grow to a larger size annealing at temperature 600°C. Upon further up 1100°C, gradually disappear. Raman-scattering enhancement phonon mode approximately 575cm−1 P+ implantation, which is induced by production oxygen vacancies (VO). are annealed out 700°C accompanying...
Wood cellulose nanofibril films with sodium carboxylate groups prepared from a 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized pulp exhibited an extremely low oxygen permeability of 0.0008 mL μm m–2 day–1 kPa–1 at 0% relative humidity (RH). Positron annihilation lifetime spectroscopy (PALS) was used to determine the pore sizes in wood and tunicate TEMPO-oxidized (TOCN-COONa) vacuum (i.e., RH). PALS analysis revealed that size TOCN-COONa remained nearly 0.47 nm film surface interior...
Undoped ZnO single crystals were implanted with aluminum ions up to a dose of ${10}^{15}{\mathrm{Al}}^{+}/{\mathrm{cm}}^{2}.$ Vacancy defects in the layers detected using positron lifetime and Doppler broadening measurements slow beams. It shows that vacancy clusters, which are close size ${\mathrm{V}}_{8},$ generated by implantation. Postimplantation annealing S parameter increases temperature range from $200\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$...
$\mathrm{ZnO}$ crystals were implanted with $20--80\phantom{\rule{0.3em}{0ex}}\mathrm{keV}$ hydrogen ions up to a total dose of $4.4\ifmmode\times\else\texttimes\fi{}{10}^{15}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}2}$. Positron lifetime and Doppler broadening annihilation radiation measurements show introduction zinc vacancy-related defects after implantation. These vacancies are found be filled atoms. After isochronal annealing at...
The reemission yield of ortho-positronium (o-Ps) into vacuum outside mesoporous silica films on glass is measured in reflection mode with a specially designed lifetime (LT) spectrometer. Values as high 40% are found. intensity the 142ns LT recorded function depth. depth profiling correlated to 2γ and 3γ energy ones determine annihilation characteristics inside films. Positron capped used pore size. For first time, set consistent fingerprints for positronium annihilation, o-Ps vacuum, size,...
The nanoscopic structure of three kinds commercially available composite membranes (LF10, NTR729HF, and NTR7250) for water purification has been studied by energy-variable positron annihilation. consist a functional polymer film porous polysulfone substrate supported on nonwoven polyester fabric. Positron annihilation γ-ray lifetime techniques were employed to probe the layer subnanometer-sized free-volume holes in films, respectively. It was found that LF10 contains two different layers...
Native defects in Si-doped AlGaN grown by metalorganic vapor phase epitaxy were probed monoenergetic positron beams. Doppler broadening spectra of the annihilation radiation and lifetimes measured, these compared with results obtained using first-principles calculation. For AlxGa1−xN (4 × 1017 Si/cm3), vacancy-type introduced at above x = 0.54, this was attributed to transition growth mode Stranski-Krastanov mechanism from Frank-van der Merwe mechanism. Al0.6Ga0.4N, vacancy concentration...
Defects in GaN grown using metalorganic chemical vapor deposition were studied through the use of monoenergetic positron beams. For Mg-doped GaN, no large change diffusion length positrons was observed before and after activation Mg. This attributed to scattering by potentials caused electric dipoles Mg–hydrogen pairs. Si-doped line-shape parameter S increased as carrier density increased, suggesting an introduction Ga vacancy due Fermi level effect. Based on these results, we discuss...
Quasi-monochromatic photons of energies 1.6-8.7 MeV have been generated by the Compton backscattering laser light on relativistic electrons in TERAS storage ring. The spectra backscattered measured with an anti-Compton spectrometer system. present system has a 155-cm/sup 3/ coaxial-type pure-Ge detector as central and well-type NaI(Tl) scintillator 8-in phi *8-in outer one. With usual anticoincidence technique, clear photopeak were obtained suppression ratio 2-4. maximum energy spread show...
Solutions of Nafion® with an ion exchange capacity (IEC) 0.91 meq g−1, which are on the verge formation SO3H nanoclusters, were spin coated silicon (Si), glassy carbon (GC) and platinum/silicon (Pt/Si) substrates to form films up 256 nm thickness. Nanostructure was studied using Doppler broadening annihilation radiation (DBAR), positron lifetime (PAL), X-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM) contact angle measurements. Contact angles as low 10 degrees indicate...
A method for enhancing the brightness of an intense slow positron beam produced by electron linear accelerator (LINAC) in order to obtain microbeam was developed. The developed enhancement system is simple and consists only a few optics transmission remoderator. LINAC magnetically guided from source experimental room. extracted magnetic field focused lens on remoderator enhance its brightness. brightness-enhanced sample lens. size at 90 μm, which two orders magnitude smaller than that...
Diffusion of ortho-positronium ($o$-Ps) in mesoporous silica films with different pore morphologies and its emission from the surfaces were studied using Ps time-of-flight method positron annihilation $\ensuremath{\gamma}$-ray energy spectroscopy. Probabilities $o$-Ps formation are almost same films, however, intensity film much larger cagelike pores is significantly less than that smaller tubelike pores, where diffusion between cages feasible by tunneling. A simple strategy suggested to use...
Positron annihilation lifetime and Doppler broadening of radiation experiments are performed in a polyurethane film using the mono-energetic slow positron probe as function energies. Significant variations signals observed at short distance from surface . The ortho-positronium polymer increases near surface, while its intensity decreases. results consistent with description free-volume hole model for positronium formation proposed by Brandt, Berko Walker. This study further confirms that...
In this paper, we report the thermalization process of positronium (Ps) in various mesoporous silica/hybrid silica films with pore surfaces decorated by different groups, such as -OH, -H, and -$\mathrm{C}{\mathrm{H}}_{3}$, studied Ps time-of-flight measurement. Thermalization pores -OH -H was found to be more efficient than -$\mathrm{C}{\mathrm{H}}_{3}$. This can understood from point view that rates upon collisions these groups are due their effective masses. Therefore, our observation...